During a surprise trip to Baghdad, U.S. Defense Secretary Ash Carter announced that the U.S. will deploy another 560 troops to Iraq -- bringing the total U.S. troop levels authorized for the country to 4,647.

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The additional troops will deploy in the coming days and weeks and will provide infrastructure and logistical support to the Qayyarah airfield, about 40 kilometers south of Mosul.

Earlier in the day, Carter said that U.S. and coalition forces will use the airfield, recently seized by Iraqi Security Forces, as a logistical hub in advance of the upcoming battle for ISIS-held city of Mosul.

“With the retaking of Qayyarah West airfield, the Iraqi Security Forces have once again demonstrated a serious will to fight,” Carter said in a press release. “I congratulate them on their recent successes and reaffirm that the United States, along with our coalition partners, will continue to do all we can to support Iraq’s effort to serve ISIL a lasting defeat.”

According to the Department of Defense, President Obama approved the deployment of the additional U.S. troops upon Carter’s recommendation after consulting with Joint Chiefs of Staff Chairman Gen. Joseph Dunford; Gen. Joseph Votel of the U.S. Central Command; and the commander of Operation Inherent Resolve, Lt. Gen. Sean MacFarland.

“These additional U.S. forces will bring unique capabilities to the campaign and provide critical enabler support to Iraqi forces at a key moment in the fight,” Carter said.

Last month, the Iraqi government recaptured the city of Fallujah after a five-week campaign. Fallujah was the first city taken by ISIS in January 2014.

After the retaking of Fallujah, the Iraqi government was able to set its sights on Mosul, Iraq’s second-largest city. However, American officials have cautioned that given current logistical shortfalls, an offensive is not likely this year.

President Obama had earlier this year authorized a troop increase to 4,087 in Iraq, although official troop numbers have not reached that threshold and currently remain at about 3,700.

Why us Qayyarah Important?

The successful Iraqi military offensive on Fallujah may have received most of the world's attention, but another Iraqi offensive in northern Iraq taking place around the same time has been just as important. Iraqi troops backed by coalition airstrikes have pushed on the town of Qarayyah, located about 25 miles south of Mosul. American military officials have described the town as "an intermediate step on the way to Mosul," similar to how Makhmur has become a staging area for Iraqi military offensives pushing north to retake ISIS-held villages in the Tigris River Valley.

The additional American troops will head to the Qarrayah air base, located outside the town, that was seized by Iraqi military forces this weekend. Its airstrips and base perimeter should allow for the quick arrival of material and support that would make it a logistical hub for the ongoing operations in Qarrayah and beyond.

The base known as "Q-West" has been a key Iraqi target for some time because it could serve as a supply and logistical hub not only for the Iraqi military as it pushes north, but for the additional American military advisers and support teams that would be needed for the eventual offensive on Mosul.

Does This Mean an Offensive on Mosul Will Happen Soon?

Ash Carter said Monday that the new American troops headed to Qayyarah would arrive within days and weeks, a move to quickly seize a tactical opportunity against ISIS, which has continued to lose territory in Iraq and Syria.

The new American support for Qayyarah is a way to build on the momentum gained by the Iraqi victory in Fallujah. American military officials were surprised at how quickly Iraq's military was able to seize Fallujah from ISIS just weeks after Iraq's government made a surprise decision to retake the city. The overall operation to liberate the ISIS-held city took five weeks, but the city came under Iraqi control just 10 days after the troops entered the city's center and initially encountered heavy ISIS resistance.

But it remains unclear if the victory in Fallujah and the retaking of the Qayyarah air base means that the timetables for retaking Mosul have been accelerated.

American officials have said that they realistically did not expect an offensive on Mosul to occur this year. The main effort of the U.S. and coalition training of Iraq's military has been to build up the 25,000 Iraqi troops that would be needed for an offensive on Mosul. Officials have telegraphed that the offensive to retake Iraq's second largest city from ISIS would require at least five Iraqi military brigades moving on the city from the south and an additional two brigades of Kurdish Peshmerga fighters pushing from the north.

More than likely the quick build-up of Iraqi and U.S. military personnel at Qayarrah will facilitate that larger offensive down the road by creating a shorter supply line for Iraqi troops as they continue moving north.